The present invention relates to a side clamp for use in a saw regrinding machine for holding a circular saw blade in place during a sharpening operation without scratching or marring the painted or coated surface of the blade.
Manufacturers of saw blades for commercially available products of the type commonly sold in hardware stores now require that these saw blades be painted or coated with TEFLON.RTM. (polytetrafluoroethylene) prior to sharpening. It is important for appearance sake that the finish or coating not be scarred or scratched since the saw blade will be displayed in packaging for purchase by a retail consumer. It is necessary, however, to sharpen the saw blade after it has been painted or coated since the paint or coating would dull the edges of the blades if applied after sharpening.
Most saw regrinding machines are of the type that sharpen a saw blade by applying side clamps to the blade from either side, sharpening a particular tooth, and then indexing the saw blade, allowing it to slide over the side clamps before the clamps are tightened to sharpen the next tooth in sequence. This is a problem with most saw regrinding machines because when the saw is clamped by the side-to-side clamps, enough pressure remains on the saw blade while indexing to cause the clamps to scratch the coating on the blade's surface.
Usually the clamps are made of metal so as to be rigid enough to hold the saw blade in place while it is being sharpened. Some manufacturers have tried to overcome the problem of scratching by using a hard plastic material as a side clamp. The hard plastic, however, does not have enough lateral strength to prevent the saw blade from bending or shifting during the regrinding process, and this impairs the accuracy of the sharpening operation.
Typically the side clamps that are used in commercial saw regrinders are two side-by-side clamps, one on either side of the saw blade, having a diameter of about one inch to an inch and a half. During sharpening the clamps are applied to the surface of the saw blade with a pressure of about 150 lbs from either side. The pressure is then partially released to exert only about one to ten pounds on the saw blade while it is indexed by a finger or some other common type of indexing mechanism. There must be enough friction from the side clamps to keep the saw blade from spinning freely so that the indexing mechanism will accurately align the next tooth in sequence for sharpening.
Therefore, friction must be continuously applied to the saw blade by the side clamps, but the side clamps will scratch the painted or coated surface of the saw blade as it rotates during indexing.